Centrifugal partition chromatography (CPC) is a method of separating compounds of a mixture between a mobile phase and a stationary phase for each of which the compounds have a different affinity. Known chromatography devices have a stack of flat rings which are rotated about their axis of symmetry and which each have, in a plane perpendicular to this axis, a multitude of cells connected to one another by inlet/outlet ducts or channels for example engraved in these rings. The stationary phase is held immobile inside cells by means of the centrifugal force to which it is subjected due to the rotation of the rings, whilst the mobile phase percolates the stationary phase. Reference may be made, for example, to document FR-A-2 791 578 for the description of such a device.
These devices have a significant gain in productivity, compared to high performance liquid chromatography (HPLC) devices having a packed column, especially due to the following advantages:                absence of solid stationary phase (relatively expensive), with instead a liquid stationary phase, the regeneration or replacement of which can be carried out in a very short time; and        significantly higher ratio of stationary phase, which retards the undesirable appearance of nonlinear phenomena and is expressed by a proportional increase of the capacity of the column enabling the elution of compounds at increased concentrations with an inversely proportional mobile phase consumption.        
In recent years it has been sought to improve the efficiency of these CPC devices in order to optimize the separations obtained, knowing that this efficiency is essentially based on the flow of the mobile phase through the stationary phase. The effect of the Coriolis acceleration generated by the rotation of the rings on the two-phase flows observed in the cells has thus been demonstrated, as presented, in particular, in the article Mass Transport and Flow Regimes in Centrifugal Partition Chromatography, by L. Marchal, J. Legrand, A. Foucault, AlChE J., 48 (2002) 1692. More specifically, each cell may be divided into three zones comprising an inlet zone where the dispersion of the mobile phase originating from the inlet channel in the form of droplets must be favored, an intermediate zone of curvilinear movement of these droplets and an outlet zone where the coalescence of the droplets before the transfer of the mobile phase into the outlet channel must be favored.
The appended FIGS. 2 and 3, which refer to the aforementioned document FR-A-2 791 578, illustrate the usual arrangement of the two inlet/outlet channels 11 and 12, 11′ and 12′ of each cell 10, 10′ relative to a radial straight line D of the corresponding ring 3, 3′ that passes through its axis of rotation X′X and through the barycentre G of the cell 10, 10′. It is seen in FIG. 2 that the two inlet/outlet orifices 11a and 12a via which these channels 11 and 12 open respectively into each cell 10 are both located on this radial straight line D of the ring 3 and, in FIG. 3, that the two inlet/outlet orifices 11a′, 12a′ of each cell 10′ of the ring 3′ are located on either side of this straight line D (also visible in FIGS. 2 and 3 are the two inlet and outlet cells 10a and 10b of the ring 3, 3′).
In a known manner, a flow of liquid from the radially outer side towards the radially inner side of each cell (i.e. from the periphery toward the center) represents, for the stack of rings, an upflow, whereas conversely a flow toward the radially outer side of each cell (i.e. from the center toward the periphery) represents a downflow, the flow direction being determined by the ratio of the masses of mobile phase and of stationary phase.